问题
I managed to execute a single command through ssh with Jsch but when i try to execute a second command it fails
For debugging i brought this problem down to this lines:
import java.io.IOException;
import java.io.InputStream;
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
public class Exec {
public static void test(Session session) throws Exception {
Channel channel = session.openChannel("exec");
((ChannelExec) channel).setCommand("pwd");
channel.setInputStream(null);
((ChannelExec) channel).setErrStream(System.err);
InputStream in = channel.getInputStream();
channel.connect();
byte[] tmp = new byte[1024];
while (true) {
while (in.available() > 0) {
int i = in.read(tmp, 0, 1024);
if (i < 0)
break;
System.out.print(new String(tmp, 0, i));
}
if (channel.isClosed()) {
System.out.println("exit-status: " + channel.getExitStatus());
break;
}
try {
Thread.sleep(1000);
} catch (Exception ee) {
}
}
channel.disconnect();
}
public static void main(String[] arg) {
try {
JSch jsch = new JSch();
Session session = jsch.getSession("nck", "127.0.0.1", 22);
session.setPassword("asd");
session.setConfig("StrictHostKeyChecking", "no");
session.connect();
test(session); // This one succeeds with exit-status: 0
test(session); // This one fails with exit-status: 255
session.disconnect();
} catch (Exception e) {
//
}
}
}
This is mostly the official Exec example but this gives me this output:
/home/nck
exit-status: 0
exit-status: 255
The first command is executed succesfully the second doesnt.
Any Ideas ?
回答1:
Hey I have exactly the same problem with jsch and Ubuntu. (How) did you solve it? Making a new session for every execute eats too much time? At the moment I catch the jsch exception and search for "session isn't down" then I reconnect the session and execute command again. That works but is not a good solution.
Edit: I was on the wrong way I solved my problem for now by using
channel = session.openChannel("shell");
instead of "exec".
回答2:
Here is a complete working Java class based on @krishna's answer:
/**
* Run several ssh commands in a single JSch session
*/
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import java.io.*;
class SshMultiCommands
{
public static void main(String[] args) throws Exception
{
JSch jsch = new JSch();
String user = "user"; //CHANGE ME
String host = "192.168.222.157"; //CHANGE ME
String passwd = "password"; //CHANGE ME
int port = 22;
Session session = jsch.getSession(user, host, port);
session.setPassword(passwd);
session.setConfig("StrictHostKeyChecking", "no");
session.connect();
Channel channel = session.openChannel("shell");
OutputStream ops = channel.getOutputStream();
PrintStream ps = new PrintStream(ops, true);
channel.connect();
InputStream input = channel.getInputStream();
//commands
ps.println("ls -lag");
ps.println("cd /etc");
ps.println("ls");
ps.println("exit");
ps.close();
printResult(input, channel);
channel.disconnect();
session.disconnect();
}
/**
* @param input
* @param channel
*/
private static void printResult(InputStream input,
Channel channel) throws Exception
{
int SIZE = 1024;
byte[] tmp = new byte[SIZE];
while (true)
{
while (input.available() > 0)
{
int i = input.read(tmp, 0, SIZE);
if(i < 0)
break;
System.out.print(new String(tmp, 0, i));
}
if(channel.isClosed())
{
System.out.println("exit-status: " + channel.getExitStatus());
break;
}
try
{
Thread.sleep(300);
}
catch (Exception ee)
{
}
}
}
}
回答3:
you can use shell to execute multiple commands. following is the code to execute commands via shell.
Channel channel=session.openChannel("shell");
OutputStream ops = channel.getOutputStream();
PrintStream ps = new PrintStream(ops, true);
channel.connect();
ps.println("mkdir folder");
ps.println("dir");
//give commands to be executed inside println.and can have any no of commands sent.
ps.close();
InputStream in=channel.getInputStream();
byte[] bt=new byte[1024];
while(true) {
while(in.available()>0) {
int i=in.read(bt, 0, 1024);
if(i<0)
break;
String str=new String(bt, 0, i);
//displays the output of the command executed.
System.out.print(str);
}
if(channel.isClosed())
break;
Thread.sleep(1000);
channel.disconnect();
session.disconnect();
}
回答4:
I used exactly same code and had problem some of the times reading output of the script i executed through ssh. Sometimes the program was missing the all content, and sometime only a part of the content. I resolved my problem by changing the if(channel.isclosed) in the nested loop. Here is the new code
while (true) {
while (in.available() > 0) {
int i = in.read(tmp, 0, 1024);
if (i < 0)
break;
System.out.print(new String(tmp, 0, i));
}
if (channel.isClosed()) {
if(in.available() > 0) {
int i = in.read(tmp, 0, 1024);
System.out.print(new String(tmp, 0, i));
}
System.out.println("exit-status: " + channel.getExitStatus());
break;
}
try {
Thread.sleep(1000);
} catch (Exception ee) {
}
回答5:
If you want to use exec. you can run multiple commands by putting a semi colon (;) within commands
like:
pwd;ls- -l;
cd foldername
((ChannelExec) channel).setCommand("pwd;ls -l; cd foldername");
回答6:
This wasn't a bug in jsch, it was a bug of my ssh server (cygwin - I bet I configured something wrong...)
Edit: hmm I had the same problem with jsch with Ubuntu ... weird
Guess as workarround I'll have to open a new session for each query.
来源：https://stackoverflow.com/questions/7207688/jsch-one-session-multiple-channels